There are numerous residential and commercial environments having phones wired in parallel. In this familiar mode of operation, each of the phones rings in response to an incoming call, each of the phones may be used to answer the incoming call, and each of the phones may concurrently participate in an ongoing call by simply going off-hook. As illustrated in FIG. 1, a telephone system includes a plurality of conventional analog phones 120, 121 with handsets 130, 131 that may be wired in parallel directly to the Public Switch Telephone Network (PSTN) 100 or indirectly via a Private Branch Exchange (PBX) 110 or comparable server system and communications links 152, 154, 155 with conductor pairs commonly known as tip and ring lines. In a hotel, for example, the PBX (a) facilitates sharing of particular number of PSTN trunks with a relatively larger number of guest lines or phones, (b) supports room-to-room calling without involving the public network, (c) tracks phone usage so that guests may be billed for their telephone usage, and (d) enables/disables phone operation upon guest check-in/check-out from a room.
Illustrated in FIG. 2 is a typical sequence diagram for two analog telephone phones operating in parallel, although the operation applies more generally to three or more analog phones coupled in parallel. When an incoming call request, e.g., RING signal 202, 204, originating from the PBX 110 or PSTN, for example, arrives at and is answered by a first phone, an off-hook signal 206-207 is sent back to the PBX 110. Telephone voice signals 210-212 and subsequently transmitted between the PBX or PSTN and between the phone and associated phone handset 130. If a second phone 121 sharing a common tip and ring lines with the first 120 is off-hooked 216 during the ongoing conversation, audio signals are also exchanged between the second analog phone and its associated handset 131. If the first telephone 120 on-hooks before the second analog phone 121, the first handset voice signal 222 and the voice signals 228, 230 continue to be exchanged with the second telephone handset even though the first phone initially answered the call. Eventually the second phone 121 on-hooks 232 and the call is terminated.
With the rapid onset of Internet Protocol (IP) telephony into the marketplace, commercial institutions including hotels are motivated to upgrade existing analog telephone systems with IP telephones to enhance functionality and services not available with analog phones systems. With IP telephony operating data lines, hotel guests may be provided Internet access, caller-ID display, text message delivery, setup of wake-up calls, room service, account status, automatic checkout, and the like. In a number of instances, however, it is desirable for the hotels to replace some but not all guest analog phones with IP phones. For example, a hotel may wish to replace the analog phone at a hotel room's desktop with an IP phone while retaining the legacy analog phone commonly situated at the side of one or more beds as well as those analog phones at or near a bathroom.
While private branch exchange (PBX) systems have been adapted to support both IP and analog phones, there is currently no way to operate an IP phone and analog phone in parallel. Therefore, there is a need for a system and method to efficiently and cost effectively operatively couple IP and analog phones for paralleled voice communications.